1. Field of the Invention
The present invention relates to a laser irradiation apparatus and method of fabricating an organic light emitting display using the same and, more particularly, to a laser irradiation apparatus including a mask having means for changing a propagation path of a laser beam irradiated from a laser generator and a method of fabricating an organic light emitting display using the same.
2. Description of the Related Art
In general, an organic light emitting display, which is a flat panel display, includes an anode, a cathode, and organic layers between the anode and the cathode. The organic layers include at least an emission layer. The organic layers may further include a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer, in addition to the emission layer. The organic light emitting display may be classified into a polymer organic light emitting display and a small molecule organic light emitting display depending on the organic layer, particularly, a material that forms the emission layer.
In order to realize a full color organic light emitting display, it is required to pattern the emission layer. A method of patterning the emission layer includes a method using a shadow mask in the small molecule organic light emitting display, and an ink-jet printing method or a laser induced thermal imaging (hereinafter, referred to as LITI) method in the polymer organic light emitting display. With the LITI method, it possible to finely pattern the organic layer. The LITI method may be used to manufacture large, high resolution displays. Advantageously, the LITI method is a dry process, unlike the ink-jet printing that is a wet process.
FIG. 1 is a cross-sectional view illustrating a method of forming an organic layer pattern using an LITI method.
Referring to FIG. 1, a donor substrate 120 where an organic layer 130 is formed is laminated on a substrate 110 where a predetermined element is formed. When a laser beam 150 is irradiated on a predetermined region of the donor substrate 120 having the organic layer 130, the laser beam 150 is absorbed by a light-to-heat conversion layer of the donor substrate 120 and then converted to thermal energy, which allows the organic layer 130 forming a transfer layer to be transferred onto the substrate 110, thus patterning the organic layer on the substrate 110. In this case, the organic layer 130 is separated from the donor substrate 120 by the thermal energy, and is transferred onto the substrate 110 while bonding within the organic layer 130 is broken. Energy required to break the bonding within the organic layer 130 should be higher than energy required to allow the organic layer 130 to be broken from the donor substrate 120 and transferred. Dotted portion indicate portions where the bonding within the organic layer 130 is broken.
FIGS. 2A and 2B are a schematic view and a beam profile illustrating a method of fabricating an organic light emitting display using a conventional laser irradiation apparatus.
Referring to FIG. 2A, a donor substrate 120 having an organic layer 130 is laminated on a substrate 110 having a predetermined element. A laser irradiation apparatus 200 includes a laser generator 240, a patterned mask 260, and a projection lens 270. A laser beam 250 is irradiated from the laser generator 240 on a predetermined region in the donor substrate 120. At this time, the laser beam 250 irradiated from the laser generator 240 passes through the patterned mask 260 and is refracted by the projection lens 270 to be irradiated on the donor substrate 120. The laser beam 250 is blocked at an unpatterned portion of the mask 260.
The organic layer 130 on the donor substrate 120 is transferred on the substrate 110 by the laser beam 250. After the transfer process, a cathode is formed on the formed organic layer pattern to complete the organic light emitting display.
Referring to FIG. 2B, a beam profile 280 of the laser beam 250 irradiated on the donor substrate 120 is illustrated. The x-axis represents regions where the laser beam is irradiated, and the y-axis represents intensity of the laser beam. Looking into the beam profile, it is appreciated that the laser beam is irradiated over the irradiated region with uniform intensity. The intensity of the laser beam required to break the bonding in the organic layer 130 should be higher than that required to separate the organic layer 130 from the donor substrate 120 to be transferred on the substrate 110. Eventually, the laser beam having excessive intensity to transfer the organic layer is irradiated on the organic layer so that the organic layer may be damaged to thereby degrade quality of the transferred organic layer pattern.